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Friday, November 22, 2013

The word proprioception means responding to one’s self. This
is the sense that allows you to understand what your body is doing in relation
to itself. If you are told to raise your hand, you understand that your hand is
raised even when your eyes are close. That
is proprioception. Another example of
proprioception is the test police use to test for drunk driving where they ask
one to close one’s eyes and touch one’s nose. You can do this because of
proprioception.

The nerve endings for this sense are located at every joint
and in the muscles (muscle spindles) throughout the body. Proprioception develops in tandem with touch
and the receptors are in place in very early fetal development. Infants rely on
conscious proprioception a lot as they are learning new skills and learning to
control their bodies. This process is teaching their proprioceptive sense to
function on its own.

One reason that proprioception is not thought of as one of
the “senses” is because it functions mostly on an unconscious level. We are
usually most aware of it when learning a new motor task and then , when
learned, don’t think about the proprioceptive input anymore. In fact, if we
did, our movements would be labored and choppy. The article cited at the end of
this section includes a description of a man who lost his sense of
proprioception and the difficulties he faced in trying to do simple motor tasks.

Putting increased weight on the joints increases the sense
of proprioception. Stimulating proprioception is both calming and alerting
(like chocolate, which both calms and alerts, as few other things do). This is
why a hug feels so good. Aside from the social meaning, a hug stimulates the
proprioceptive system. Proprioception
has been receiving attention as it seems in recent years as it seems to be
critical in the work with and treatment of disordered sensory processing.

Kinesthesia is the sense of the movement of your body. It
seems to use the same system as proprioception but may be processed in a
different part of the brain. It was the study of kinesthesia that led to the
discovery of the sense of proprioception

Monday, November 18, 2013

Touch is not really one sense. It is made up of several
different senses which have different nerve endings and different response
areas in the brain. In other words, they are processed individually though we
lump them all together and call them touch. These include light touch, deep pressure, heat
, cold and pain receptors. What they
have in common is that the nerve endings are spread throughout our skin so we
can experience sensation from any part of our body. There are some areas that
have a higher concentration of nerve endings and are therefore more sensitive
than other areas of the body. Some areas of the body may have more of one kind
of receptor than others so may be more sensitive to certain types of touch than
to others but in general there are touch receptors all over the body in the
skin. Some types of receptors are around the internal organs as well. We all
know you can have a stomach ache that is not felt from the skin. All of this is
complicated by the fact that you may have different touch sensations at
different places at the same time. You mind needs to sort all the sensation and
let you decide which is the most important for you to get the information that
you need. If you remember, in the
introduction to this series, we used the example of the hot iron to illustrate
the sensory motor arc. That example uses the sense of touch, specifically,
heat, so you can see how fast your brain can select what you need to know.

The sense of touch is one of the earliest to begin to
develop, with some receptors in place by 4 weeks gestation, but it seems to
take up to 16 to 20 years for the system to be fully operational. There are at least 4 different types of receptors and miles of nerve fibers,
as well as the cognitive learning needed to distinguish from what one thing
feels like as opposed to another. The fact that you can reach into your purse
and find the keys without looking is a testament to the development of your
sense of touch.

Simple touch is anything but! The simplest sensation is
pressure, but as noted, light pressure and deep pressure are registered
differently. Next would come vibration, followed by recognition of different
textures, sizes, shapes and spatial orientation, which can all be recognized by
touch. Research indicates that awareness
of pressure and vibration is present at birth. Size recognition seems to begin
early, perhaps 2-4 months but is on a basic level and need refining. There is
some recognition of different textures by 4-6 months which continues to be
refined over the next 10 years. The recognition of shape difference by touch
may begin after 6 months and there are indications that this, too, continues to
develop during childhood.

Early tactile exploration is often by mouth, as this is a
very sensitive area for touch stimulation. Manual exploration actually begins
around 4 months of age and continues to improve through childhood. The ability
to recognize objects by touch is pretty much the same from 15 to about 50 years
of age but as with other senses, there is a decline during the aging process, just as touch is one of the first senses to
develop it is the last to decline.

Touch is probably the most pervasive sense we have. It is
everywhere in our bodies and is difficult to occlude. Just as development
impact the sense of touch (learning shapes, textures etc.), there is ample
evidence that touch impacts development.
Studies of infants who were deprived of a chance to use their sense of
touch, who were not held or whose physical contact was limited to the crib they
were lying in, suggest that this caused global delays that were difficult to
make up. Of course, the sense of touch, along with the next two we will
discuss, underlies all motor abilities